Screwdriver

ABSTRACT

A screwdriver having a replaceable blade that preferably is slit in its longitudinal direction with the two shanks thus formed being resilient and having their free end portions lying in different geometrical planes so as to facilitate retaining a screw merely by introducing the free ends of said blade into the slot of the screwhead.

United States Patent Tore L. Hill Carl Tunbergs vag 9, 171 53 Solna, Sweden 211 App]. No. 848,294

[ 72] Inventor [22] Filed Aug. 7, 1969 [45] Patented Jan. 11, 1972 [32] Priority Aug. 14, 1968 [33] Sweden [54] SCREWDRIVER 4 Claims, 5 Drawing Figs.

[52] U.S. Cl 145/50 E [51] Int. Cl Bb 15/00 [50] Field of Search 145/50,

[5 6] References Cited FOREIGN PATENTS 934,665 III 948 France l/50.4 236,236 0/1925 Great Britain. l45/50.l 259,902 6/1949 Switzerland /50 Primary ExaminerWilliam S. Lawson Assistant Examiner-Michael Koczo, Jr. Anomey-Sughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT: A screwdriver having a replaceable blade that preferably is slit in its longitudinal direction with the two shanks thus formed being resilient and having their free end portions lying in different geometrical planes so as to facilitate retaining a screw merely by introducing the free ends of said blade into the slot of the screwhead.

PATENTED .mu 1' m2 31 633639 SCREWDRIVER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to screwdrivers having replaceable blades and more particularly to a device for attaching a displaceable screwdriver blade to the end ofa screwdriver.

2. Description of the Prior Art In conventional screwdrivers the problem often occurs, that the blade of the screwdriver is exposed to a certain extent of wear in use, which may result in it being flattened or deteriorated in other manner. Furthermore, it is generally not possible to vary the thickness and the width, respectively, of the screwdriver blade, and therefore it is sometimes necessary to work with a blade that in unduly thin or narrow with respect to the slot in the screwhead. On other occasions, a screwdriver may have a blade that is so thick that it cannot be accommodated in the slot of the screwhead. If the screwdriver blade is too thin with respect to the slot of the screwhead it may occur that both the screwdriver blade and the screwhead are damaged when a resistive screw is turned, and in addition the screwdriver may then easily slip out of the slot of the screwhead. Moreover, it is normally not possible to attach a screw to a screwdriver in such manner that the screwdriver may be rotated to arbitrary spatial orientation with the screw being retained on the screwdriver, whereas if the screwdriver has a blade that is so thick that it cannot be accommodated in the slot in the screwhead, the screwdriver will no longer be of use. Also, the disadvantage sometimes occurs that with screwdrivers having long shafts the entire shaft will rotate so that the resulting force will be reduced and the torque will be poor.

SUMMARY OF THE INVENTION This invention proposes to eliminate the above-mentioned disadvantages, and this is achieved by providing the foremost portion of a screwdriver with a slit, into which a replaceable screwdriver blade may be introduced and may be retained by slidable locking means. The screwdriver blade may be split in its longitudinal direction by means of a longitudinal slit, with the free ends of the shanks thus formed being located in different geometrical planes with respect to each other. Furthermore, the screwdriver blade may be adapted to extend in front of the foremost end of the shaft of the screwdriver in locked position substantially a distance corresponding to the depth of the slot of a screwhead intended for being engaged by the screwdriver.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described more specifically below with reference to the accompanying drawing, in which:

FIG. I is an exploded view of the components forming the front end ofa screwdriver designed in accordance with the in vention,

FIG. 2 illustrates the front end of the screwdriver assembled and with the screwdriver blade introduced into the slot of a screw,

FIG. 3 is an elevational view of the front portion of the screwdriver, partially in cross section,

FIG. 4 is a front view of the foremost portion of the screwdriver, and

FIG, 5 is a plan view of the foremost portion of the screwdriver, also partially in cross section.

The same designations have been utilized for identical parts in the individual figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. I the designation 1 refers to the foremost end of the shaft of a screwdriver in accordance with the invention, with said foremost end being provided with a groove having the form of a slit up to the dashed line 4. The designation 2 refers to a replaceable screwdriver blade having two shanks 5 and 6,

respectively, which are separated by a slit 7 terminating at a wider portion 8 of the screwdriver blade, with said wider portion uniting said shanks. The free ends of the shanks 5, 6 are situated in different horizontal planes with respect to each other. The designation 3 in FIG. I refers to a slotted lockring or sheath, which appropriately may be knurled at its front end so as to provide a good grip, with said lockring being intended to be urged onto the screwdriver shaft over the screwdriver front end 1 with the screwdriver blade 2 introduced into the above-mentioned slit at the foremost end of the screwdriver so as to affix the screwdriver blade in said slit with the right end (as viewed in FIG. 1) of portion 8 engaging the material of the screwdriver shaft at the dashed line 4. Hence, lockring 3 will retain screwdriver blade 2 in the screwdriver and will facilitate replacement of said blade. As has been indicated above, the foremost ends of the two shanks 5 and 6, respectively, of the screwdriver blade 2 are slightly displaced with respect to each other, with one of them being positioned higher than the other one. This is illustrated more specifically in FIG. 4, with the free portions of the shanks being designated 9 and I0, respectively, Thus, in the illustrated example the foremost ends of said shanks are situated in mutually parallel planes which are separated from the horizontal plane, but said ends may also be located in mutually parallel planes forming an angle to the horizontal, or otherwise they may be positioned in any arbitrary appropriate manner so that when they are introduced into the slot of a screwhead they engage the edges of the slot so as to affix the screw to the screwdriver. Furthermore, the front ends of the shanks may be tapered as indicated in FIGS. 3 and 4, respectively.

FIG. 2 shows the front end of the screwdriver assembled with the lockring 3 slid onto the spindle or screwdriver shaft 1 and adapted to resiliently clamp the replaceable screwdriver blade 2 in the spindle 1. In FIG. 2, the two end portions 9 and 10,-respectively, (compare FIG. 4) of the screwdriver have been introduced into the slot 11 of the screwhead 12 of a screw 13, thereby retaining the screw 13 on the screwdriver as the result of the resilient action of the shanks 5 and 6, respectively, of the screwdriver blade 2.

The lockring 3 and the front end of the screwdriver shaft 1 are adapted to cooperate in such manner, that when lockring 3. has been slid onto shaft 1 to the greatest possible extent, with the limit being set by a taper 16 on the lockring, the screwdriver blade 2 will project to such a degree in front of a taper 17 on the shaft 1, that only a predetermined length of the screwdriver blade can be introduced into the slot of the screwhead before the latter strikes the edge of the shaft 1 with its portion lying outside the slot. Hereby optimal torsional strength of the screwdriver blade 2 is achieved, with said blade being tightly clamped in shaft 1 very close to the front end of the screwdriver blade as the result oflockring 3.

FIG. 3. shows the front portion of the screwdriver shaft 1 on an enlarged scale, with the lockring 3 slid on and being adapted to clamp the front ends of shaft 1 around screwdriver blade 2. As may be seen from said figure, spindle 1 may, if desired, be provided with a circular recess 14, and lockring 3 may be provided with a corresponding bulge 15 adapted to be urged into recess 14 when the lockring is slid on. As may be seen from FIG. 3 the front ends of screwdriver shaft 1 may be provided with flat portions 18 for engaging the screwhead in operative position.

FIG. 5 illustrates the front end of the screwdriver as viewed from above, partially in cross section, with one shank 5 of the screwdriver blade 2 being clearly shown, whereas shank 6 is hidden behind the knurled portion of lockring 3.

Because of the possibility of easily and quickly replacing the screwdriver blade 2 in accordance with this invention it is always feasible to work with a blade having a width and a thickness, respectively, corresponding to the slot in the screw to be utilized. If the blade is worn, it is not necessary to reject the entire screwdriver, as it is sufficient to introduce a new blade. The fact that only a short portion of the screwdriver blade extends in front of the screwdriver shaft provides for a strong force and thus adequate torque.

The screwdriver blade does not necessary have to be provided with the slot 7, nor it is necessary that the front ends 9 and 10, respectively, of the screwdriver blade be located'in different planes with respect to the horizontal, although this is appropriate so as to retain the screw, as the result of the resilient action in the shanks of the screwdriver blade, independently of the orientation of the screwdriver in space, i.e., independently of how the screwdriver is rotated and turned, respectively.

As an alternative to the embodiment described above, the blade 7 and lockring 3 may be preassembled into one single integral unit.

The invention is not limited to the embodiments described above and illustrated in the drawing, and it may be utilized in other appropriate connections.

lclaim:

l. A screwdriver assembly for engaging a slot of predetermined depth in a screwhead, comprising:

a. a screwdriver shaft having a central slot in one end 'thereof,

b. a replaceable screwdriver blade member having a longitudinal slot in one end forming two spaced, resilient shanks having tips for engaging a slot in a screwhead, said shanks being bevelled on opposite tip sides, the other end of the blade member having opposed, outwardly projecting shoulders and adapted to be inserted in the central d. a slideable locking collar having opposed longitudinal slots in its sides adapted to receive the shoulders when assembled, the collar being adapted to fit over the end of the screwdriver shaft to retain the blade member in its inserted position in the central slot.

2. A screwdriver assembly as claimed in claim 1 wherein the central slot and blade member are so dimensioned that the tips of the shanks extend from the central slot, when the blade member is inserted therein, a distance approximately equal to the depth of a slot of a screwhead intended to be engaged by the shanks.

3. A screwdriver assembly as claimed in claim 2 wherein:

a. the shaft and collar have circular cross sections,

b. the inner surface of the collar is provided with at least one protrusion,

c. the shaft has an annular groove to accommodate the protrusion in a locking relationship when assembled, and

d. the end of the shaft has opposed, tapering faces that converge toward the shank tips.

4. A screwdriver assembly as claimed in claim 1 wherein:

a. the shaft and collar have circular cross sections,

b. the inner surface of the collar is provided with at least one protrusion,

c. the shaft has an annular groove to accommodate the protrusion in a locking relationship when assembled, and

d. the end of the shaft has opposed, tapering faces that converge toward the shank tips. 

1. A screwdriver assembly for engaging a slot of predetermined depth in a screwhead, comprising: a. a screwdriver shaft having a central slot in one end thereof, b. a replaceable screwdriver blade member having a longitudinal slot in one end forming two spaced, resilient shanks having tips for engaging a slot in a screwhead, said shanks being bevelled on opposite tip sides, the other end of the blade member having opposed, outwardly projecting shoulders and adapted to be inserted in the central slot in the screwdriver shaft, c. the spaced shanks being biased to lie in different, offset geometrical planes with respect to each other, and d. a slideable locking collar having opposed longitudinal slots in its sides adapted to receive the shoulders when assembled, the collar being adapted to fit over the end of the screwdriver shaft to retain the blade member in its inserted position in the central slot.
 2. A screwdriver assembly as claimed in claim 1 wherein the central slot and blade member are so dimensioned that the tips of the shanks extend from the central slot, when the blade member is inserted therein, a distance approximately equal to the depth of a slot of a screwhead intended to be engaged by the shanks.
 3. A screwdriver assembly as claimed in claim 2 wherein: a. the shaft and collar have circular cross sections, b. the inner surface of the collar is provided with at least one protrusion, c. the shaft has an annular groove to accommodate the protrusion in a locking relationship when assembled, and d. the end of the shaft has opposed, tapering faces that converge toward the shank tips.
 4. A screwdriver assembly as claimed in claim 1 wherein: a. the shaft and collar have circular cross sections, b. the inner surface of the collar is provided with at least one protrusion, c. the shaft has an annular groove to accommodate the protrusion in a locking relationship when assembled, and d. the end of the shaft has opposed, tapering faces that converge toward the shank tips. 